1. Field of the Invention
This invention relates generally to a magnet switch, and more particularly to an improved magnet switch so designed as to form a more efficient magnetic circuit for a contact-drive plunger. The switch of this invention is used, for example, for controlling electric power supplied to a starter motor for starting an engine.
2. Description of the Prior Art
An engine mounted on an automobile is started by a starter motor. To this starter motor, electric power is supplied through a switch mechanism when an ignition switch is operated. A magnet switch is applied to the above switch mechanism, such as shown in U.S. Pat. No. 4,887,056. The magnet switch is supplied with drive electric power when the ignition switch is operated.
In the magnet switch, a plunger is provided in opposed relation to a stationary core, and an exciting coil wound on a bobbin is provided so as to surround the plunger. A frame made of a magnetic material is provided so as to surround the exciting coil. One end portion of this frame is connected to the stationary core, and the other end portion of the frame is disposed close to the outer peripheral portion of the plunger. With this arrangement, a magnetic circuit connecting the stationary core, the frame and the plunger to one another is constructed.